Automatic dialing apparatus



Filed NOV. 18, 1964 3 Sheets-Sheet 1 i- N 4 2 Ill 40 Z 001-. on OJ 0:r9333 7 m: m: .I

INVENTOR. R PEG 0 TA ATTO RN EY Dec. 17, 1968 w. PEco'rA 3,411,207

AUTOMATIC DIALING APPARATUS Filed NOV. 18, 1964 3 Sheets-Sheet 2INVENTOR. WA R PE C OTA ATTORNEY Dec. 17, 1968 w. PECOTA 3,417,207

AUTOMATIC DIALING APPARATUS Filed Nov. 18, 1964 3 Sheets-Sheet 5 FIG. 4

INVENTOR.

WALTER PECOTA BY I 1/ ATTORNEY .7

United States Patent 3,417,207 AUTOMATIC DIALING APPARATUS WalterPecota, Mountain Lakes, N.J., assignor to G-V Controls Inc., LivingstonTownship, N.J., a corporation of New Jersey Continuation-impart ofapplication Ser. No. 382,040,

July 13, 1964. This application Nov. 18, 1964, Ser.

16 Claims. (Cl. 179-90) ABSTRACT OF THE DISCLOSURE A plurality of digitconductors (d in number) and a plurality of address conductors (c innumber) control an array of ncd normally open electric paths, eachcombination of one digit conductor and one address conductor whencontemporaneously activated effecting the closure of a respective n ofthe paths. As an incident to activation. of an address conductor thedigit conductors are successively activated thereby successively toclose, n at a time, ml of the paths. Such closures render meanseffective to variously interconnect the terminals of an electricalsystem which transmits integer-representing signals as determined by theterminal interconnection.

This application is a continuation-in-part of my copending applicationSer. No. 382,040, filed July 13, 1964, which has been abandoned sincethe filing of this application.

This invention relates to automatic dialing apparatus, and moreparticularly to dialing apparatus by which a multi-digit telephoneaddress may be dialed in response to the manipulation of a singlecontrol-e.g. the depression of a single button. The term telephoneaddress is used herein to denote what is commonly referred to astelephone number, in order to avoid confusion with the use herein of theword number in its elementary sense. The term dialing is used in thebroad sense of commanding a connection with the telephone at aparticular telephone address, without limitation to the specific senseof manipulating a dial at such.

There is in use manual dialing apparatus provided with a bank ofinteger-representing buttons, typically ten in number, with which amulti-digit telephone address may be dialed by successive depression ofthe buttons respectively corresponding to the successive integers ofthat adresse.g., if that address be 112-3580, by successive depressionof the buttons labelled 1, l, 2, 3, 5, 8 and 0. Such apparatus is of avariety of types; in general, however, each of those types involves theuse of an electrical system, for the selective transmission of a numberof respective-integer-representing signals, which includes a pluralityof variously interconnectible terminals, it being the particularinterconnection of those terminals existing at any time which determinesthe integer which will at that time be represented by the signaltransmitted from that electrical system.

The procedure of successive depression of d buttons (d being the numberof digits to be dialedin the example just given, seven), obviouslyaffords the opportunity to dial any desired telephone address whateverof d digits. It does, however, impose on the user a burden which is fargreater and which, except in the hands of a telephone operator or otherperson who by constant dialing develops unusual proficiency, is farslower and more prone to error, than that which would be imposed by aneed to depress only one button for a given telephone address. There aremany specialized commercial or professional situations in which the vastmajority of calls are made to a limited number only of telephoneaddresses, or in which 3,417,207 Patented Dec. 17, 1968 "ice (e.g. in a2- or even a 3-digit PBX or other intercommunication system) the totalnumber of telephone addresses to be dealt with is finite. In either ofthese situations the overall burden on the user may be greatly reduced,speed greatly increased and propensity to error minimized, by the use ofautomatic apparatus which causes the successive dialing of all 0! digitsof a telephone address in response to the depression of a single button(or the like) appropriate to that addresssuch apparatus beingpermissably supplemented by the manual apparatus above described, sothat any telephone address not provided for by a respective singlebutton may still be dialed manually. It is to the provision of suchautomatic apparatus that this invention is particularly directed.

While not in all aspects limited thereto, the invention has especialutility and has been employed with great success in connection with anelectrical system (such as is now available to telephone subscribers incertain communities) in the form of a tone-dialing oscillator, inparticular one which is arranged to transmit a dual-frequency tone andin which the terminals abovementioned are arranged in two sets, theinterconnections of the terminals of each set determining a respectiveone of the two frequencies of that tone.

In one aspect the invention comprises, in combination with an electricalsystem such as above described, d (d being a plural integer) digitconductors; c (c being a plural integer) selectively activatable addressconductors; ncd (n being an integer) normally open electrical pathsunder the control of said digit conductors and said address conductors,each combination of one digit conductor and one address conductor whencontemporaneously activated etfectingthe closure of a respective n ofsaid paths; means, actuated as an incident to activation of one of theaddress conductors, for successively activating the digit conductors ina predetermined sequence; and terminal-interconnecting means, with whichthe paths are selectively connected to render thoseterminal-interconnecting means efiective in accordance with closures ofthose paths, for establishing preselected interconnections of theterminals of the first-mentioned electrical system.

Various more detailed aspects are comprised in the invention. Thus theremay be provided means, connected with the digit-conductor-activatingmeans and responsive to the completion of its operation, fortie-activating the previously activated address conductor.

The electrical system abovementioned may be a tonedialingaudio-frequency oscillator and the interconnection of its terminalsabove referred to may determine its tone output. Its terminals maycomprise s (s being a plural integer) sets each of a plurality ofvariously interconnectible terminals, and n above referred to may equals. There may if desired be provided means to which a selected one of thepaths may be connected for disabling the oscillator during the closureof that selected path, or both during that closure and during anyremainder (after that closure) of the sequence of digit-conductoractivation.

A pulse generator may be provided, and the means for sucessivelyactivating the digit conductors may comprise electronic-steppingswitchmeans timed by that pulse generator. There may be provided means, timedby the pulse generator in multiple with the electronic-stepping-switchmeans, for periodically activating and deactivating the oscillator.Telephone receiver and transmitter elements may be locally connectedwith the oscillator and there may be provided means, timed by the pulsegenerator in multiple with the electronic-steppingswitch means, foraltering the efficiency of action of at least one of those elements.There may be interposed between the pulse generator and theoscillator-activating and deactivating means a means for retarding thetiming of the latter relative to that of the electronic-stepping-switchmeans.

Allied and other objectives and aspects of the invention will appearfrom the following detailed description and the appended claims.

In that detailed description reference is had to the accompanyingdrawings, in which:

FIGURE 1 is a schematic diagram of one embodiment of an automaticdialing apparatus according to the invention, the electrical systemwhose terminals are to be variously interconnected and the pulsegenerator each being indicated by a respective box;

FIGURE 2 is a schematic diagram of a typical pulse generator such asreferred to above;

FIGURE 3 is a schematic diagram of a typical tonedialing oscillatorwhich may form the electrical system above referred to; and

FIGURE 4 is a schematic diagram of another form of the electrical systemabove referred to, together with portions of the automatic dialingapparatus (such as shown in FIGURE 1) modified appropriately to thedifferent form of electrical system.

Since in the embodiment of FIGURE 1 the electrical system above referredto is a tone-dialing audio-frequency oscillator, such an oscillator mayfirst be briefly described. In principle such an oscillator couldgenerate ten different single-frequency tone out-puts, then beingprovided for example with a single set of variously interconnectibleterminals whose interconnections would determine the oscillators toneoutput. In practice it has been found by others that a preferableapproach is to cause the oscillator to generate dual-frequency toneoutputs, the oscillator then being typically provided with two sets ofvariously interconnectible terminalsthe interconnections of theterminals of the first set determining the lower-frequency component,and the interconnections of those of the second set determining thehigher-frequency component, of the tone output. A typical design of suchan oscillator has been detailedly described in an article by J. H. Hamand F. West of Bell Telephone Laboratories, Inc. presented at theA.I.E.E. Winter General Meeting of January- February 1962 as Paper No.62-227. In FIGURE 3 of the drawings I show an oscillator of designessentially similar to that of FIGURE 3 of that article, integrated withthe transmitter T and the receiver or earphone E of a standard telephoneset.

It will be understood that if s be the number of sets of variouslyinterconnectible terminals, then s in the tonedialing oscillatorillustrated in FIGURE 3 will be two.

Briefly, the positive and negative conductors of the telephone line areconnected to respective terminals N and N and, when the cradle switch Sis closed, to respective terminals RR and C on the conventional network4258, under which circumstances the network terminal B will inter aliabe somewhat more positive than N and the network terminal R will interalia be still more positive. A p-n-p transistor Q whose collector isconnected to the negative terminal C, is the amplifying element of theoscillator. The requisite feedback is provided by two ferrite-coretransformers whose primaries B and A and a resistor R are seriallyconnected between the emitter of Q and the network terminal R, and whosesecondaries B and A and a resistor R are serially connected between thebase of Q and the network terminal B. A capacitor C is connected betweenthe base and the collector of Q and a varistor RV is connected betweenthe primary and secondary returns (embracing R but not R The oscillatoris of course intended to function only during the action of tonedialing; to place it otherwise out of operation the primary return isbrought through a pair X of normally open contacts which will be closedonly during each tone output.

The tuning of the lower-frequency component of the oscillator output isaccomplished in the circuit of a tertiary winding A provided on thefirst transformer, and that of the higher-frequency component in thecircuit of a tertiary winding B provided on the second transformer,these tertiaries being connected in series with each other. Each of thetwo tertiaries is provided with three taps, and in each instance thetuning is effected by connecting a capacitor between the junction of thetertiaries and a selected one of the taps or, in the case of thetertiary A, alternatively across the entire tertiary. A capacitor fortuning the tertiary A is shown as Ca and one for tuning the tertiary B'as Cb. A first terminal of each is connected to the junction joining thetwo tertiaries; tuning of the lower-frequency component then requiressimply the connection of the second terminal of Ca to one of the taps onA or alternatively to its non-common extremity, while tuning of thehigher-frequency component requires simply the connection of the secondterminal of Cb to one of the taps on B.

The non-common extremity of A may be connected to a terminal L1, theadjacent tap to a terminal L2, the next tap to a terminal L3 and theremaining tap to a terminal L4; the tap on B nearest its non-commonextremity may be connected to a terminal H1, the next tap to terminal H2and the remaining tap to a terminal H3. To tune the lower-frequencycomponent to its lowest frequency terminal L0 may be connected toterminal L1, to tune that component to the next higher frequency L0 maybe connected to terminal L2, to tune to the next higher frequency L0 maybe connected to terminal L3, and to tune the lower-frequency com-ponentto its highest frequency L0 may be connected to terminal L4; to tune thehigher-frequency component to its lowest frequency H0 may be conected toterminal H1, to tune that component to its intermediate frequency H0 maybe connected to terminal H2, and to tune that component to its highestfrequency H0 may be connected to terminal H3. Thus L0 and L1 and L4 formone set of terminals to be variously interconnected, while H0 and H1through H3 form a second set of terminals to be variouslyinterconnected, to determine the oscillators dual-frequency tone output.

As brought out in the article above referred to, the oscillation of theoscillator at two frequencies simultaneously is made possible byremoving from the transistor Q the task of amplitude limitation of theoscillations and thus permitting that transistor to operate over anessentially linear portion of its characteristic, and by otherwise andseparately performing the amplitude-limit ing tack for each of the twofrequency components. As in the disclosure of that article, amplitudelimitation for the lower-frequency component may be effected by avaristor RVa shunted between the non-common extremity of tertiary A andthe adjacent one of the taps, and for the higher-frequency component maybe effected by a varistor RVb shunted between the first and second tapsof B (reckoned from the common terminal).

For purposes later apparent it may be desirable to provide on theoscillator a terminal N, which will be connected with the negativeterminal N when the cradle switch S is closed.

In the normal use of the telephone the earphone E is to be connecteddirectly across the network terminals R and GN, but during the operationof the oscillator it is desirable that this connection be through anattenuating resistor R accordingly the connection of the earphone acrossthe network terminals is made through R but that resistor is normallyshorted out by a pair Z of normally closed contacts which will be openedduring operation of the oscillator. In the normal use of the telephonethe transmitter T is connected directly across the network terminals Rand B, but during the operation of the oscillator it is desirable thatthis connection be open-circuited; accordingly the connection of thetransmitter across the network terminals is made through a pair V ofnormally closed contacts which will be opened during operation of theoscillator. In order to shockexcite each of the tuned circuits formed bythe tertiaries A' and B with the capacitors which will have beenrespectively shunted across selected portions of each (byinterconnection of L0 with one of the terminals L1 through L4 and of H0with one of the terminals H1 through H3), it is desirable that at theinception of a tone output there be interrupted a direct currentotherwise flowing through those tertiaries; to provide for such acurrent the tertiaries may be serially connected between networkterminals RR and R, and to provide for such interruption this connectionmay be made through a pair U of normally closed contacts which will beopened during operation of the oscillator.

As brought out in the references to which the article abovementionedrefers, the frequencies made available for the lower-frequency componentof the oscillator output may desirably be approximately 697, 770, 852and 941 cycles per second, and those made available for thehigher-frequency component may desirably be approximately 1,209, 1,336and 1,477 cycles per second. As further there brought out, pairs ofthose frequencies may be used to signify various integers in accordancewith the following:

Terminals eon- Lower Higher For the integer nected to frequencyfrequency L0 and H0 L1 H1 697 1, 209 L1 H2 697 1, 336 L1 H3 697 1, 477L2 H1 770 l, 209 L2 H2 770 l, 336 L2 H3 770 1, 477 L3 H1 852 1, 209 L3H2 852 1, 336 L3 H3 852 1, 477 L4 H2 941 1,336

When the oscillator is performing its function of gencratingsimultaneously oscillations of the two frequencies, its dual-frequencyoutput appears across the terminals N and N and will be impressed acrossthe telephone line connected to those terminals. If by the oscillatorthere be generated a series of dual-frequency tone outputs portraying amulti-digit number to be dialed, then through the intermediary of remotetelephone-equipment circuitry itself known and forming no part of thepresent invention that number will be tone-dialed.

Except as specifically noted above, the foregoing description withrespect to FIGURE 3 presents information contained in the article abovereferred to (to which reference may be had for further details) and ispresented not to describe the present invention but rather to explain atypical environment with which it may be utilized.

A typical embodiment of my invention itself is illustrated in FIGURE 1,in combination with the abovedescribed tone-dialing oscillator of FIGURE3 (which in FIGURE 1 appears simply as a box designated TDO, withterminals designated and arranged similarly 0t those of FIGURE 3). InFIGURE 1 one other circuit component a pulse generator with one-stageamplifieralso is shown as a box, designated PG, and typical internalcircuitry of that pulse generator is shown in FIGURE 2 hereinafterdescribed. The apparatus of FIGURE 1 is intended to be powered by a DC.supply (not shown) which provides an unregulated positive potential(typically 26 volts) and a lower regulated positive potential (typically15 volts). For simplicity circuit points intended to be connected to thenegative terminal of that supply are terminated in a single small circlecontaining a circuit points intended to be connected to the regulatedpositive potential are terminated in a single small circle containing aand circuit points intended to be connected to the unregulated positivepotential are terminated in a pair of side-byside small circles eachcontaining a Otherwise than as stated in this paragraph, FIGURE 1 is acomplete schematic illustration in its own right.

While the invention may be arranged to tone-dial telephone addresseseach of any number d digits, FIGURE 1 for simplicity illustrates thatnumber d as three. The invention makes use of a number c of addressconductors each of which is normally utilizable for the tone-dialing ofa respective preselected telephone address, but there may be specialcases wherein a particular telephone address to be tone-dialed has anumber of digits greater than d and then more than one address conductorwill be utilized for the tone-dialing of that designation; FIGURE 1arbitrarily illustrates the number 0 as four, but with two of the fouraddress conductors utilized for the tone-dialing of one telephoneaddress of more than d digits (so that the number of telephone addressesavailable to be tone-dialed with the particular illustration of FIGURE 1is three).

For the first digit, whatever the integer of which it in any particulartelephone address may consist, there is provided a digit conductor 1,for the second digit there is provided a digit conductor 2, and for thethird digit there is provided a digit conductor 3 (and more would beprovided to increase the number of digit conductors to d if that weremore than the illustrated three). For the tone-dialing of a firsttelephone address to be preselected, there is provided an addressconductor 10; for the tone-dialing of a second telephone address to bepreselected, there is provided an address conductor 20; for a thirdtelephone designation to be preselected, there is provided an addressconductor 30; and there is provided a fourth address conductor 40 whichcould be appropriate to a fourth telephone address to be preselected,but in the illustrated embodiment is employed to increase the number ofdigits of which the third telephone address may be composed.

With each available combination of one digit conductor and one addressconductor there may be electrically associated a number n of paths. Thenumber n will, of course, be at least one, and would desirably be one ifthe number s (above defined) were one. In the illustrated embodiments ofthe inventions is (as above noted) two, and in the particular circuitryillustrated in that embodiment it is convenient to make n equal tosi.e., two.

Thus for the combination of digit conductor 1 and address conductor 10there may be provided two paths 113 and 114. Electrically to associatethese paths with the digit conductor 1 they may respectively includepairs 171 and 172 of contacts which are normally open but are closed,upon activation of the digit conductor 1, by the action of a relay 170in which those contact pairs are comprised and whose coil is connectedto that conductor. Electrically to associate the paths 113 and 114 withthe address conductor 10 they may respectively include pairs 111 and 112of contacts which are normally open but one closed, upon activation ofthe address conductor 10, by the action of a relay 11 in which thesecontact pairs are comprised and whose coil may be connected between thatconductor and the negative supply potential.

For the combination of digit conductor 2 and address conductor 10 theremay be provided two paths 213 and 214. Electrically to associate thesepaths with the digit conductor 2 they may respectively include pairs 271and 272 of contacts which are normally open but are closed, uponactivation of the digit conductor 2, by the action of a relay 270 inwhich those contact pairs are comprised and whose coil is connected tothat conductor. Electrically to associate the paths 213 and 214 with theaddress conductor 10 they may respectively include pairs 211 and 212 ofcontacts which are normally open but are closed, upon activation of theaddress conductor 10, by the action of relay 11 abovementioned of whichthose con-tact pairs form additional parts.

For the combination of digit conductors 3 and address conductor 10 theremay be provided two paths 313 and 314. Electrically to associate thesepaths with the digit conductor 3 they may respectively include pairs 371and 372 of contacts which are normally open but are closed, uponactivation of the digit conductor 3, but the action of a relay 370 inwhich those contact pairs are comprised and whose coil is connected tothat conductor. Electrically to associate the paths 313 and 314 with theaddress conductor 10 they may respectively include pairs 311 and 312 ofcontacts which are normally open but are closed, upon activation of theaddress conductor 10, by the action of relay 11 abovementioned of whichthose contact pairs form still additional parts.

There have thus been described nd (i.e., six, n being two and a beingthree) paths 113, 114, 213, 214, 313 and 314 associated with addressconductor 10, through the medium of nd respective contact pairs (111,112 312) all forming parts of relay 11; the n paths 113 and 114 areassociated with digit conductor 1 through the respective contact pairs171 and 172, the n paths 213 and 214 are associated with digit conductor2 through the respective contact pairs 271 and 272, and the n paths 313and 314 are associated with digit conductor 3 through the respectivecontact pairs 371 and 372. In an entirely corresponding manner 11d paths123, 124, 223, 224, 323 and 324 are associated with address conductorthrough the medium of nd respective contact pairs (121, 122 322) allforming parts of relay 21; the n paths 123 and 124 are associated withdigit conductor 1 through the abovementioned contact pairs 171 and 172respectively, the n paths 223 and 224 are associated with digitconductor 2 through the abovementioned contact pairs 271 and 272respectively, and the n paths 323 and 324 are associated with digitconductor 3 through the abovementioned contact pairs 371 and 372respectively. Again in an entirely corresponding manner 11d paths 133,134, 233, 234, 333, 334 are associated with address conductor throughthe medium of mi respective contact pairs (131, 132 332) all formingparts of relay 31; the n paths 133 and 134 are associated with digitconductor 1 through the abovementioned contact pairs 171 and 172respectively, the n paths 233 and 234 are associated with digitconductor 2 through the abovementioned contact pairs 271 and 272respectively, and the n paths 333 and 334 are associated with digitconductor 3 through the abovementioned contact pairs 371 l and 372respectively. Finally in a quite corresponding manner nd paths 143, 144,243, 244, 343 and 344 are associated With address conductor through themedium of nd respective contact pairs (141, 142 342) all forming partsof relay 41; the n paths 143 and 144 are associated with digit conductor1 through the abovementioned contact pairs 171 and 172 respectively, then paths 243 and 244 are associated with digit conductor 2 through theabovementioned contact pairs 271 and 272 respectively, and the n paths343 and 344 are associated with digit conductor 3 through theabovcmentioned contact pairs 371 and 372 respectively.

Each of the 0 paths 113, 123, 133 and 143 may include some portion of acommon conductor 173 through which it is connected to a first contact ofthe pair 171, each of the 0 paths 114, 124, 134 and 144 may include someportion of a common conductor 174 through which it is connected to afirst contact of the pair 172 and so on, as illustrated by the furthercommon conductors 273, 274, 373 and 374. All of the cd paths 113, 213,313, 123, 223, 323, 133, 233, 333, 143, 243 and 343 may include a commonconductor 403 connected to the second contact of each of the pairs 171,271 and 371, while the remaining cd paths (having numbers respectivelyhigher by 1) may include a common conductor 404 connected to the secondcontact of each of the pairs 172, 272 and 372. As will be understood,each of the ncd paths as above described extends from above itsrespective upper contact pair (e.g. 111, 112, 211 342) to below itslower contact pair (e.g. 171, 172 372).

The result of the above described arrangements is that each of the ncdpaths above described will be effectively closed upon, but only upon,the activation of both that one address conductor and that one digitconductor with which in combination that path is electricallyassociated. In other words that path is under the control of that onedigit conductor and that one address conductor, and those conductorswhen contemporaneously activated effect the closure of that path.

Means are provided to activate a desired one of the c (eg. four) addressconductors 10, 20, 30 and 40. Such means may be comprised in an addressselector schematically illustrated, under the designation CS, in FIGURE1, in which there may be provided a conductor J to which there may betwo paths from regulated positive potentialone through a relativelylow-valued resistor 61 and a diode 62, the other through two seriallyarranged relatively high-valued resistors 64 and 63. For the illustratedfour address conductors the address selector may comprise four selectorunits 12, 22, 32 and 42, of which the selector unit 12 may first bedescribed.

Through a switch 13 operable at will a network 14 may be connectedbetween conductor I and negative supply potential; this network may forexample comprise serially a resistor 14a, a diode 14b and a resistor140, all of which may be shunted by a resistor 14d. Between conductor Jand address conductor 10 there may be placed the anode-cathode path of asilicon controlled switch (that term being hereinafter abbreviated SCS)17. Between the junction of diode 14b with resistor 14c and the negativesupply potential there may be serially connected a capacitor 15 and aresistor 16, and the cathode gate of SCS 17 may be connected to thejunction joining 15 and 16; the anode gate of the SCS 17 may beconnected to regulated positive supply potential through a resistor 18.(Simply in order to perform its basic function the network 14 need notbe as elaborate as the form illustrated and described, but that form hasbeen found desirable in order to render the address selector reasonablyproof against unfavorable influence by transients which may unavoidablybe present in the DC. supply or may be capacitatively impressed on theconductor between switch 13 and the network.)

In operation, if the switch 13 be momentarily closed a potential equalto regulated positive supply potential will be abruptly impressed acrossthe network 14, and a substantial voltage will be abruptly developedacross the resistor 14c. The wavefront incident to the latter will beimpressed through capacitor 15 on the cathode gate of SCS 17; since theanode of that SCS is effectively connected to regulated positive supplypotential 'at least through the resistors 63 and 64 that SCS is incondition to be fired, and it will be fired by this wavefrontimpression. The result of its firing will be the conduction of currentthrough resistor 61 and diode 62 to conductor J and from that conductorthrough the SCS 17 and address conductor 10 to and through the coil ofrelay 11this current activating that address conductor and of coursebeing more than sufficient to insure the reliable operation of the relay11.

Each entirely similar to the selector unit 12 may be the selector units22 and 32 and, were it not for the abovementioned illustrative intentionto utilize selector unit 42 for additional digits of a telephone addressfor which the (1 digits of selector unit 32 are insufficient, also thatselector unit 42the designations of the components in each successiveselector unit being progressively increased by 10. In view of thatillustrative intention selector unit 42 comprises, in place of a switchcorresponding to 13, a resistor 43, and from its network 14 there isomitted any diode corresponding to 14b; further comments as to selectorunit 42 are made hereinafter.

In operation, once the SCS of any of the selector units 12, 22, 32 and42 is fired and thus rendered conductive it will remain conductive untilthe performance of an act deliberately designed to terminate thatconductivity; the performance of such an act at an appropriate time iscontemplated, and it and the means for accomplishing it are hereinafterdescribed.

Means are provided to cause the digit conductors, once conductor 1 hasbeen activated, to be activated in the predetermined sequence which(including conductor 1) is l, 2, 3. Such means may comprise a steppingswitch (preferably electronic) of which a preferred form isschematically illustrated under the designation SS in FIGURE 1, and inwhich there may be provided a conductor K connected to regulatedpositive supply potential through a 9 resistor 71. Such a steppingswitch may comprise a number d of stages 50, 59 and 60, of which thefirst stage may first be described.

Between the conductor K and the negative supply potential there may beconnected the anode-cathode path of an SCS 51 and a resistor 55. Betweenthe cathode gate of the SCS 51 and that negative supply potential theremay be connected a resistor 52 (across which a diode 53 may be shuntedto preclude the development of excessive reverse potentials betweencathode gate and cathode). An input capacitor 54 may lead to the cathodegate of 51 from other circuitry hereinafter to be described. Fromregulated positive supply potential to the anode gate there may beconnected serially a resistor 56 and a diode 57. Across the resistor 55there may be connected the baseto-emitter path of an n-p-n transistor 58to whose collector there may be connected the digit conductor 1, towhich it was above disclosed that the coil of relay 170 would beconnected-the far extremity of that coil (along with the far extremitiesof the coils of relays 270 and 370) being connected to unregulatedpositive supply potential.

Each of the second and third stages of the stepping switch SS,designated respectively as 59 and 60, may be similar to the first stageas above described, excepting (i) that neither need contain a diodecorresponding to 53 of the first stage, and (ii) the input capacitor ofeach of those stages is connected from the junction joining the resistorand the diode which lead to the anode gate of the preceding stage (egthe junction joining 56 and 57 in the first stage 50).

An adjunct of the stepping switch SS is a pulse generator (desirablywith one-stage amplifier); such a generator, designated as PG, is shownin FIGURE 1 simply as a box with two main output terminals 541 and 542,the

latter being connected to negative supply potential, and

with a third terminal 543 which, when there is applied to it a voltagesubstantially more positive than negative supply potential, quells orsquelches the pulse generator. Typical intern circuitry of PG is shownin FIG- URE 2 and is hereinafter detailedly described; it is sufficientat this juncture, however, to note that while the pulse generatorremains squelched the potential of the output terminal 541 will besubstantially negative supply potential, that forthwith uponde-squelching that outputterminal potential will abruptly rise to manyvolts more positive than negative supply potential and will there remainfor a first period typically of 50 milliseconds, that at the end of thatperiod that output-terminal potential will abruptly drop back tosubstantially negative supply potential and will there remain for aninterval typically of 50 milliseconds, that at the end of that intervalthat output-terminal potential will abruptly rise againand so on in aseries of SO-millisecond positive pulses separated by SO-millisecondintervals, until the pulse generator is re-squelched by thereappliaction to terminal 543 of a sustained voltage substantially morepositive than negative supply potential.

The squelch terminal 543 may be connected to the conductor K mentionedabove, through a resistor 72 and one or more diodes 73; so long as onlyinfinite or high irn pedance intervenes between the conductor K andnegative supply potentialwhich is the case in the quiescent contion ofthe apparatusthe conductor K will be at a potential close to regulatedpositive supply potential, and by the above-described connection of itto the terminal 543 there will then be applied to that terminal asquelching potential.

Between the output terminal 541 to the pulse generator and negativesupply potential there may be serially connected a capacitor 74 and aresistor 75, and across the resistor 75 there may be serially connecteda diode 76 and a resistor 77; across the resistor 77 there may beconnected the base-toemitter path of a n-p-n transistor 80 of which thecollector is connected to the conductor K. The result of the circuitrydescribed in this paragraph is that each time the terminal 541 abruptlyrises in potentiali.e. at the beginning of each positive pulse from thepulse generatorthe transistor (i.e. its collector-toemitter path) willbe momentarily rendered conductive.

The application of a positive wavefront to the cathode gate of the SCS51, through the input capacitor 54, will trigger the operation of theapparatus described in the last preceding six paragraphs, the initialresult of that application being to fire SCS 51 so that current flowsfrom conductor K to negative supply potential through that SCS andthrough the base-to-emitter path of transistor 58 (whosecollector-to-emitter path is thus rendered conductive.) This SCS firingreduces the potential of conductor K to little over a volt abovenegative supply potential, thus desquelching the pulse generator toresult forthwith in the first positive pulse at terminal 541.(Simultaneously with the onset of the first pulse there Will tend tooccur, as brought out in the last preceding paragraph, a momentaryconductivity of the transistor 80 but this occurrence, in connectionwith the first pulse only, is foreclosed by means hereinafterdescribed.)

The conductivity of SCS 51 and of transistor 58 will persist through-outthe SO-millisecond first pulse and throughout the succeedingSO-millisecond inter-pulse interval. At the onset of the second pulsethere will occur a momentaary conductivity of transistor 80, whichmomentarily will divert suflicient current from SCS 51 so that theremnant current through the latter falls to less than holding current,causing that SCS to extinguish and the associated transistor 58 toresume its normally non-conductive state. That SCS extinguish'mentcauses the anode gate of that SCS, and thus the junction joiningresistor 56 and diode 57, to execute an abrupt rise in potential, andthe resulting positive wavefront at that junction is applied through theinput capacitor of the stepping-switch stage 59 to result in the firingof that stages SCS and conductivity of that stages transistor. Theconductivity of the second-stage SCS and transistor Will persistthroughout the SO-millisecond second pulse and the succeedingSO-millisecond interval-but at the onset of the third pulse that SCSwill be extinguished and that transistor rendered again non-conductive,and the third stages SCS will be fired and its transistor renderedconductive, in correspondence to the action above described for thesecond stage. At the onset of the fourth pulse the third-stage SCS willbe extinguished and the third-stage transistor rendered againnon-conductive; since there remains in the illustrated stepping switchno further stage and thus no further SCS to be fired, the potential ofconductor K will thereupon rise to near regulated positive supplypotential, thus re-squelching the pulse generator.

It will thus be understood that for the first milliseconds following theapplication of a positive wavefront to the cathode gate of SCS 51 thefirst-stage transistor 58 will be conductive and digit conductor 1 thusbrought to near negative supply potential, for the second 100milliseconds the transistor of the second stage 59 will be conductiveand digit conductor 2 thus brought to near negative supply potential,and for the third 100 milliseconds the transistor of the third stage 60will be conductive and digit conductor 3 thus brought to nearly negativesupply potential. The quiescent potential of each of those digitconductors being unregulated positive supply potential (to which thecoils of relays 170, 270 and 370 are connected), this successivebringing of those conductors to near negative supply potentialconstitutes a successive activation of those conductors.

This completes the basic description of both apparatus and operation ofthe means itself for successively activating the digital conductors in apredetermined sequence.

That means is subjected to control by any one of the addressconductor-activating means (e.g. switches 13, 23, 33) and is actuated asan incident to activation of any of the address conductors. For any oneof the selector units 12, 22 and 32 this may be facilitated by the useof a common p-n-p transistor 65 whose emitter is connected to regulatedpositive supply potential, whose collector is connected to negativesupply potential through two serially arranged resistors 66 and 67, andwhose base is connected to the junction of the above-mentioned twoserially arranged resistors 63 and 64 connected between conductor I andregulated positive supply potential. The stepping-switch input capacitor54 is connected to the junction of 66 and 67. Quiescently conductor I isat regulated positive supply potential, no current flows throughresistors 63 and 64, and transistor 65 is non-co-nductive but closure ofany of the switches 13, 23 and 33 to activate the respective addressconductor, since it causes the potential conductor I to drop suddenlyand substantially, will result in an abruptly rising current throughresistor 63 and the base-to-emitter path of transistor 65, renderingthat transistor conductive and causing an abruptly rising currentthrough resistors 66 and 67 and thus an abrupt voltage developmentacross 67. From this voltage a positive wavefront is applied throughinput capacitor 54 to trigger the stepping switch and thus to invoke theaction of the means for successively activating the digit conductors inpredetermined sequence. This successive activation, occurring while oneof the address conductors stands activated, will of course result in thesuccessive closure, 11 (e.g. two) at a time, of the na (cg. six) pathswhich are under the control of that address conductor and of those (1(eg. three) digit conductors.

Attention may now be directed to the means which are provided toestablish preselected interconnections of the terminals of the setsL-L1-L2-I3-L4 and H0-H1-H2-H3 and thus to tune the two frequencies ofthe tone output of the tone-dialing oscillator TDO-the ncd paths abovedescribed being selectively connected with thoseinterconnection-establishing means to render those means effective inaccordance with closures of those paths.

In the illustrated embodiment of the invention theinterconnection-establishing means may comprise seven conductors W1, W2,W3, W4, G1, G2 and G3 respectively leading from the oscillator terminalsL1, L2, L4, H1, H2 and H3; 40d connection points each providing for theconnection of one of the four conductors W1, W2, W3 and W4 with one ofthe cd paths 113, 213, 313, 123, 223, 323, 133, 233, 333, 143, 243 and343; and d connection points each providing for the connection of one ofthe three conductors G1, G2 and G3 with one of the cd paths 114, 214,314, 124, 224, 324, 134, 234, 334, 144, 244 and 344. These 70dconnection pointstogether with another cd connection points by which aconductor M hereinafter described may be connected at will with any ofthe lastmentioned cd paths-may conveniently form a crossbar arrangement,and are collectively designated as CB. In FIGURE 1 each connection pointis illustrated as a circle intersected horizontally by the respectiveconductor and intersected vertically by the respective path; a whiteinterior of any circle designates non-connection, and a black interiorof any circle designates connection, at the point represented by thatcircle.

Individually each connection point, among those thus far described, maybe identified by the designations, used hyphenatedly, of the conductorand of the path whose connection to each other it provides for-e.g. thetop most lefthand one may be designated as W1-113, the next-tobottommost righthand one as G3344, and the bottom most righthand one as M-344(these designations, being readily determinable from the conductor andpath designations appearing in FIGURE 1, having been themselves withheldfrom application in that figure to avoid obscurement of theillustration).

Subject to later qualification in connection with the description offunction of the conductor M, it is contemplated that eaoh of the cdodd-numbered paths will be connected to some one of the four conductorsW1, W2, W3 .and W4, and that each of the cd even-numbered paths will beconnected to some one of the three conductors G1, G2 and G3. Theselection of the W and G conductors to which there will be connected thepaths having designations whose second or middle symbol is 1 will bemade in accordance with the telephone address desired to be tone-dialedupon activation of address conductor 10, that of the conductors to whichthere will be connected the paths having designations whose second ormiddle symbol is 2 will be made in accordance with the telephone addressdesired to be tone-dialed upon activation of address conductor 20, andso on. Of any such telephone address the integer of which the firstdigit consists will control the W and G conductor selections for thepaths having designations whose first symbol is 1, the integer of whichthe second digit consists will control the conductor selections for thepaths having designations whose first symbol is 2, and so on.

This may be illustrated, in connection with the first and second addressconductors or selector units, by assuming arbitarily that upon at leastmomentary closure of the first unit switch 13 it is desired to tone-dialthe telephone address 569, and that upon at least momentary closure ofthe second-unit switch 23 it is desired to tone-dial the telephoneaddress 790. For the first, it is readily determined from the tabulationearly above that in tuning of the oscillator TDO appropriate to theinteger 5 its terminals L0 and H0 should be connected to its tenminalsL2 and H2 respectively, in tuning appropriate to 6 L0 and H0 should beconnected to L2 and H3 respectively, and in tuning appropriate to 9 L0and H0 should be connected to L3 and H3 respectively; thus in theinterconnection-establishing means CB path 113 would be connected toconductor W2 and path 114 to G2, path 213 would be connected toconductor W2 and path 214 to G3, and path 313 would be connected to W3and path 314 to G3. For the second, in tuning of the oscillatorappropriate to the integer 7 terminals L0 and H0 should be connected toterminals L3 and H1 respectively, in tuning appropriate to 9 L0 and H0should be connected to L3 and H3 respectively, and in tuning appropriateto 0 L0 and H0 should be connected to L4 and H2 respectively; thus inthe interconnection-establishing means CB path 123 would be connected toconductor W3 and path 124 to G1, path 223 would be connected toconductor W3 and 224 to G3, and path 323 would be connected to W4 and324 and G2. Those connectionswhich constitute selective connections ofthe paths 113, 114, 213, 214, 313, 314, 123, 124, 223, 224, 323 and 324to render the interconnection-establishing means effective in accordancewith the closures of those pat hs-have been by way of example indicatedin FIGURE 1.

In the specific arrangements thus described each of the interconnections(between L0 and one of L1 through L4, and between H0 and one of H1through H3) which tunes the oscillator is an interconnection seriallyincluding one of the ncd paths above described (113, 114, 213 344). Itis, however, to be understood that in its broader aspects my inventionis not limited to such serial inclusion. Note is made that eachinterconnection is one which is traversable by the alternating signalcomponents which are inherently. present in the oscillators tuningcircuits.

It will now be understood that forthwith upon closure of switch 13 thetone-dialing oscillator TDO will be tuned automatically for threesuccessive units of time (each unit typically of milliseconds) to therespective three pairs of frequencies which in succession denote thepreselected telephone address 569, and correspondingly that forthwithupon closure of switch 23 that oscillator will be tuned automaticallyfor three successive units of time to the respective three pairs offrequencies which in succession denote the preselected telephone address790. Thus in a broad sense there have already been disclosed both thestructure and the operation of apparatus accomplishing a primaryobjective of the invention. It should be noted, however, that in theinterest of providing a general understanding of the overall operationat this, the earliest practicable point herein, the foregoingdescription has omitted attention to several matters to which it isdesirable to attend and detailed aspects of operation which it isdesirable to understand, as well :as certain optional features all ofwhich will now be dealt with.

For the apt functioning of the tone-dialing oscillator TDO itsabovementioned contacts X must be closed-and, because conventionaltone-dialing practice contemplates that the successive tone outputsfromthe oscillator will be each of approximately 50 milliseconds andwill be separated each from its predecessor by an interval ofapproximately 50 milliseconds, this closure should be limited to afraction only of each of the IOO-millisecond units of time lastmentioned above. To accomplish this limitation there are provided means,timed by the pulse generator in multiple with the stepping switch SS,for periodically activating and deactivating the oscillator. Such meansmay comprise a relay 88 (see FIGURE 3) of which the normally opencontacts X of the oscillator TDO form a part and 'whose coil-connectedfor example .across a pair of terminals 86 on the oscillator-may besupplied with current under the contnol of the pulse generator. Thus(see FIGURE 1) there may be provided an n-p-n transistor 85 whoseemitter may be connected to negative supply potential and whosecollector may be connected to unregulated positive supply potential viathe terminals 86 so that, when flowing, the transistors collectorcurrent will actuate the relay 88. The base of the transistor '85, whichmay be connected to negative supply potential through an appropriateresistor 84, may be connected to the output terminal 541 of the pulsegenerator, preferably through one or more voltage-dropping diodes 83.Thus basically the transistor 85 will be rendered conductive, and itscollector current caused to flow, only during the 50 millisecond pulsesthroughout which terminal 541 is substantially positive; the oscillatorTDO will accordingly be activated essentially at the onset, and will bedeactivated essentially :at the termination, of each of those pulses.

As has been pointed out by others in connection with a tone-dialingoscillator such as TDO, it is desirable that the tuning of theoscillator which is to prevail during any tone output thereof havealready been established at the instant of activation of the oscillator.To accomplish this in the present apparatus there may be interposedbetween the pulse generator PG and the relay 88-preferably betweenterminal 541 and the diodes 83a delay circuit, comprising for example aseries resistor 81 and a shunt capacitor 82, which retards for a fewmilliseconds or so the operation of the relay 88 relative to the onsetof the pulse at terminal 541.

In the early description of the tone-dialing oscillator there weredisclosed (along with their functions) three pairs of contacts Z, V andU normally closed but opened during actual operation of the oscillator.These pairs of contacts may form parts of a relay 87 whose coil may beconnected in parallel with that of relay 88, so that the opening andclosing of these contact pairs may occur simultaneously with the closingand opening of the contact pair X of the latter relay. Another detailwith respect to the contacts and relays is that across the paralleledcoils of the relays there may desirably be shunted a transient-absorbingdiode 89, in accordance with wellknown relay practice.

Attention may now be re-directed to the address selector CS and itsoperation. In the earlier description thereof there was not indicatedthe manner in which there might be accomplished the extinguishment ofany fired one of the SCSs therein at the conclusion of the operation ofthe stepping switch SS invoked by the firing of that SCS. One manner ofeifecting that extinguishment which I have employed is the capacitativeimpression, on the junction between resistor 61 and diode 62, of astrong negative pulse derived from the rise of potential of theconductor K at that conclusion-that impression momentarily interruptingthe flow of current through that diode to the conductor I; this manner,however, exhibits the conceivalbe disadvantage that if through anyconceivable mischance (such as a fortuitous manipulation of one of theswitches 13, 23, etc. at a critical instant) a channel-selector SCSbecome fired after the stepping switch SS has concluded its operationbut without re-invoking such operation, then there would be nosubsequent rise of conductor-K potential on which to rely for theaction.

Preferable for the performance of this extinguishing function is the useof an n-p-n transistor whose emitter may be connected to negative supplypotential and whose collector may be connected to the junction betweenthe abovementioned resistor 61 and diode 62. To the base of thetransistor 90, which itself may be connected to negative supplypotential through a resistor 93, there may be made a connection from theconductor K through a resistor 91 and one or more voltage-droppingdiodes 92.

It is true that in the quiescent condition of the apparatus, when theconductor K has a substantial positive potential, the transistor 90 willbe conductive and the path 61-62 thus disabled from supplying current tothe conductor J, but as above noted the path 64-63 supplies sufiicientcurrent to that conductor to permit firing (even though not holdingfired) of any one of the selector unit SCS s-and the above-describeddropping of potential of the conductor K forthwith upon that firing,since it renders the transistors 90 non-conductive, removes thedisabling influence from the path 61-62. Obviously the disablinginfluence will be re-imposed by the transistor 90 when the conductor-Kpotential rises at the end of the stepping-switch sequence, with theintended effect of extinguishing any address selector SCS which at thattime is standing fired.

It may be noted that even though the selector unit switch (e.g. 13, 23,33) associated with that SCS be still held closed this extinguishmentwill not be followed by a refiring of that SCS-for the associatedcapacitor (e.g. 15, 25, 35) will then not yet have been permitted toreadjust its charge so as to be again capable of invoking the firing ofthat SCS.

While obviously each of the third and fourth selector units 32 and 42may be used (in a manner quite analogous to that disclosed for each ofthe selector units 12 and 22) in the tone-dialing of respective thirdand fourth preselected telephone address (analogous to the typical 569and 790), they have instead been shown as used together in thetone-dialing of a telephone address of more than d (e.g. more thanthree) digits. For this purpose (as already noted) the switch of earlierselector units has in selector unit 42 been replaced by a resistor 43;to the junction joining 43 with the network 44 there may be connected'from the anode gate of the third unit SCS 37 a diode 39 poled toconduct positive current toward that anode gate. The result of theseconnections it that while the third-unit SCS 37 remains fired (during astepping-switch sequence previously initiated by the closure of switch33) the then-low potential of its anode gate will effect the essentialdischarge of the input capacitor 45 of the fourth selector unitbut thatwhen that anodegate potential a-brouptly rises on extinguishment of theSCS 37 the charging of that capacitor 45 will result in a substantialdrop across resistor 46 and the momentary application to the cathodegate of the fourth-stage SCS 47 of a pasitive potential, to result inturn in the firing of that SCS 47 and'an activation of the addressconductor 40 in response to the extinguishment of the SCS 37 or thedeactivation of the address conductor 30.

coincidentally the abrupt rise of potential of the 43-44 junctionincident to SCS-37 extinguishment may be applied to the cathode gate ofthe first-stage SCS 51 of the stepping switch SS, to initiate anautomatically repeated operation of that switch immediately followingthe conclusion of the one which had been invoke-d by switch- 33 closure,through an appropriate network 49. This network 49 may for examplecomprise a resistor 49a, capacitor 4% and resistor 490 connectedserially from the 4344 junction to negative supply potential, and adiode 49d connected from the 49b49c junction to the SCS51 cathode gate.

Let it be assumed that the telephone address in whose tone-dialing thethird and fourth address conductors are to be jointly used has a numberd+1 (eg. four) of digitsby way of arbitrary example, that it is thetelephone address 1327. The third address conductor may be used in thetone-dialing of the first three digits 132, and accordingly path 133will be connected to conductor W1 and 134 to G1, path 233 will beconnected to conductor W1 and 234 to G3, and path 323 will be connectedto conduct-or W1 and 334 to G2. The fourth address conductors may beused in the tone-dialing of the fourth digit 7, and accordingly path 143will be connected to conductor W3 and 144 to G1.

It will now be understood that upon closure of the switch 33 actionswill occur in smooth succession as follows: (i) the SCS 37 will be firedand while it so remains "132 will be tone-dialed, and (ii) the SCS 47will be fired and in the first 100 milliseconds (usefully, in the first50 milliseconds) thereafter the remaining digit 7 will be dialed.Obviously if the remainder of the telephone address to be tone-dialed bythe third and fourth address conductors jointly had been of a full d(e.g. three) digits, then appropriate connections would have been madeof paths 243, 244, 343 and 344 and a full Zd-digit number would havebeen tone-dialed.

In the d-l-l-digit (e.g. 4-digit) example just given there remain, afterthe desired telephone address has been tone-dialed, 200 milliseconds ofoperation of the stepping switch, during which two further pulses willbe generated at the terminal 541 and the oscillator TDO (in the absenceof measures to the contrary) will be twice more activated anddeactivated. During such further activations the oscillator would notproduce any of its normal tone outputs, in view of the non-connection ofpaths 243, 244, 343 and 344 with any one of the W and G conductorsbut itmay generate, to the annoyance of the user (who may hear in his earpieceE) and may send out over the telephone line connected to terminals N andN (to the possible detriment of the functioning of remote apparatus) anarbitrary high-pitched tone output. Positively to preclude this I havefound it desirable to incorporate muting arrangements which disable theoscillator from generating any tone output during the further pulse orpulses remaining after the intended telephone address has beentone-dialed. Obviously such arrangements would also be desirable in acase wherein one of the uncombined address selector units (e.g. 12 or22) was desired to be used in the tone-dialing of a telephone address ofless than d digits.

The muting arrangements may be incorporated in theinterconnection-establishing means CB, in which for example there may beincluded an eight conductor M arranged ot be connectible at will toappropriate ones of the path 111, 112, 211 344. In the particularcircuitry disclosed herein it is sufficient, in order to provide for themuting of any digit of the telephone address commanded by any addressconductor, to make the conductor M connectible either to anyodd-numbered or to any even-numbered one of those paths; in FIGURE 1 itis shown as connectible to any even-numbered one,

While the apparatus whose action is controlled by the muting conductor Mmay take any of a variety of forms, I have found particularlyadvantageous one in which (i) the disabling of the oscillator iseffected by forestalling the closure of the oscillators contacts X, forexample by disabling of the relay 88 which would otherwise close them,and (ii) the connection of the conductor M to disable the oscillatorduring closure of any one of the paths will also disable the oscillatorduring any remainder, after such closure, of the usual sequence ofdigit-conductor (egg. 1, 2, 3) activation.

For this purpose there may be employed an SCS 100, whose anode gate maybe connected with its anode through a resistor 98, whose anode may beconnected to regulated positive supply potential through a resistor 99,and whose cathode may be connected to negative supply potential. Betweenthe cathode gate of SCS 100 and negative supply potential there may beconnected the secondary of a pulse transformer 94, so that the SCS 100will be fired upon the passage of a pulse through the primary of thattransformer. That primary may be connected between the conductor M and apoint in the oscillator TDO having, under conditions of non-operation ofthe relays 8887, a DC. potential substantially different from that ofthe junction between tertiaries A and B"for example to the terminal Nmentioned early above. If now the terminal H0 be at any time connectedto the conductor M, then the oscillator capacitor Cb will be charged,from the potential of that point, through the primary and a pulse willbe passed through the primary to fire the SCS 100.

If a connection has previously been made, as illustrated, between path244 and conductor M, then when the stepping switch SS completes at 271the closure of the path 244 during the sequence invoked by the firingSCS 47i.e. at the completion of the first 100 milliseconds of thatsequence, at which time the tone-dialing of the typical telephoneaddress 1327 has already been completeda momentary pulse will be passedthrough the primary of transformer 95, and the resulting pulse acrossthe secondary will fire the SCS 100.

The base circuit of the transistor 85, preferably at the junctionbetween diodes 83 and resistor 81, may be clamped down to the anode ofthe SCS 100 through a diode 97, with the result that while the SCS 100stands fired the transistor 85 will be rendered incapable of being madeconductive, the relays 8 8 and 87 forestalled from operating, and theoscillator TDO thus kept diabled. This state of 'afiairs, beinginitiated at the time last specified in the preceding paragraph, arisesin ample time, in view of the delay circuit 8182, to render whollyineffective on the oscillator the second pulse of the sequence; sincethe SCS will still remain fired, it renders the third pulse likewiseinetfective-without requiring any connection between path 344 andconductor M.

The SCS 100 must of course be extinguished at the conclusion of thesequencefor which purpose advantage may be taken of the fact that atthat conclusion the potential of the conductor K abruptly rises. Thusfrom that conductor to negative supply potential there may be connecteda circuit serially comprising a diode 101 and two resistors 102 and 103,and to the junction between those resistors there may be connected thebase of an n-p-n transistor 105 whose emitter may be connected tonegative supply potential. The collector of the transistor 105 may besupplied with current from regulated positive potential through aresistor 107 and diode 106, and a capacitor 108 may be connected fromthe junction joining that resistor and that diode to the anode of theSCS 100.

During any sequence of operation of the stepping switch SS the conductorK will be at a low potential, the transistor 105 non-conductive, and thelefthand plate of capacitor 108 therefore at essentially regulatedpositive supply potential. But when at the conclusion of the sequencethe potential of conductor K a bruptly rises the lefthand plate ofcapacitor 108 will be abruptly brought down almost to negative supplypotnetial through the diode 106 and the abruptly-dropping impedance ofthe collector-to-emitter path of transistor 105, and a strong negativepulse will be applied by the capacitor 108 to the anode of the SCS 100to extinguish the latter. (If it were desired to extinguish the firedone of the selector unit SCSs capacitatively that could be done in anentirely analogous manner.)

Advantage may be taken of the transistor 105, which is of coursequiescently conductive, toperform the function, mentioned early above asneeding performance, of foreclosing any momentary conudctivity of thetransistor 80 at the onset of an initial pulse from the pulse-generatorterminal 541. Thus across the serially connected resistors 102-103 theremay be connected a capacitor 104 which, although it can chargeessentially instantaneously through the diode 101 upon sudden rise ofthe potential of conductor K, will discharge relatively slowly (e.g.over a period of many milliseconds) upon sudden fall of thatpotnetialwith the result that the fall of potential of conductor K whichoccurs at the onset of the first pulse only of a sequence will occurbefore there has been time for the transistor 105 to becomenon-conductive. The base circuit of the transistor 80, preferably at thejunction between capacitor 74 and diode 76, may be clamped down to thecollector of transistor 105 through a diode 109, thus foreclosing anymomentary conductivity of 80 at the onset of the first pulse.

In connection with the transistor 80 there will be noted in FIGURE 1 acircuit consisting of a capacitor 78 and a ressitor 79 connected betweenits base and regulated positive supply potnetial. This has been founddesirable to foreclose the possibility of transistor 80 being renderedmomentarily conductive (and the potential of conductor K thusmomentarily reduced) as an incident to connection of the apparatus toits source of DC. potnetial (i.e. to change of the condition of theapparatus from wholly off to quiescent).

In telephone practice it is considered desirable to test anytone-dialing oscillator from time to time to verify the operativenessand pitch of its individual-frequency outputs. In thus testing theoscillator TDO it is necessary (i) that the relays 87 and 88 betemporarily kept operated, (ii) that during the testing of anylow-frequency output no high-frequency output take place and vice versa,and (iii) that a connection be established from terminal L or H0, as thecase may be, to the individual L or H terminal appropriate to theindividual-frequency output being tested.

To provide for the most convenient accomplishment of (iii) theconductors 403 and 404 may be provided with respective branches 413 and414, in the interconnectionestablishing means CB there may be providedfour connection points at each of which the conductor branch 413 may beconnected to a respective one of the W conductors, and in that means CBthere may be provided three connection points at each of which theconductor branch 414 may be connected to one of the G conductors-itbeing understood that, (i) and (ii) being meanwhile appropriatelyaccomplished, any one such connection will elicit from the oscillator arespective one of its individual-frequency tone outputs. To accomplish(i) the upper-shown one of the terminals 86 may be temporarily connectedto negative supply potential. To accomplish (ii) while testing anylow-frequency component the conductor 414 may be connected to any two ofthe G conductors, thereby shorting some part of the tertiary B; toaccomplish (ii) while testing any high-frequency component the conductor413 may be connected to any two of the W conductors, thereby shortingsome part of the tertiary A'.

Typical internal circuitry for the pulse generator PG is shown in FIGURE2. It may be powered by the same supply as that used for the apparatuspreviously described; it may include a voltage divider formed byresistors 531 and 532 serially connected between regulated positivesupply potential and negative supply potential, at the intermediatepoint 533 of which there may be made available a positive potential of alittle over half of regulated positive supply potential.

The pulse generator may for example com-prise two n-p-n transistors 501and 502, the emitter of 501 being connected through a resistor 525, andthat of 502 being connected directly, to negative supply potential; thecollectors of 501 and 502 may be connected to regulated positivepotential through respective resistors 509 and 510.

The bases of transistors 501 and 502 may be connected to negative supplypotnetial through respective resistors 505 and 506, which may be shuntedby respective diodes 507 and 508 each poled to conduct current towardthe respective transistor base; those bases may also be connected to theintermediate-potential point 533 through respective circuits 503-519 and504-520 each serially comprising a capacitor and a diode poled toconduct current toward that point. The junction joining capacitor 503and diode 519 may be connected to regulated positive supply potentialthrough the serial combination of a high-valued fixed resistor 511 and alower-valued variable resistor 513, and that junction may also beconnected to the collector of transistor 502 through a circuitcomprising serially a resistor 515 and a diode 517 poled to conductcurrent toward that collector; the junction joining 504 and 520 may beconnected to regulated positive supply potential through the serialcombination of a high-valued fixed resistor 512 and a lower-valuedvariable resistor 514, and that junction may also be connected to thecollector of transistor 501 through a circuit comprising serially aresistor 516 and a diode 518.

A one-stage amplifier is provided by a transistor 521 whose emitter isconnected to negative supply potential, whose base is connected to theemitter of 501, and whose base-to-emitter path (rather than the resistor525) is the principal avenue for the emitted current of 501. Thecollector of transistor 521 is connected to regulated positive supplypotential through a resistor 529. The output terminals of the pulsegenerator and amplifier are constituted by 541 connected to thecollector 521, and 542 connected to negative supply potential. It willbe understood that when the transistor 501 is conductive so likewisewill be the transistor 521 and that the potential of terminal 541 willthen be little above negative supply potential; quiescently it is thisstate of affairs which is mantained by the applicaton, alreadydescribed, of a positive potential to the squelch terminal 543, which inturn is connected to the base of the transistor 501.

The conductivity of transistor 501 during the squelched condition placesthe collector of that transistor at near negative supply potential; thecircuit 516-518 then maintains the righthand plate of capacitor 504 at asimilar potential, while the resistor 506 maintains the lefthand plateof that capacitor at negative supply potentiali.e. that capacitor isessentially discharged. Transistor 502 will be non-conductive and itscollector at essentially regulated positive supply potential; thisrenders the circuit 515-517 ineffective, and a steady small current willflow through resistors 511 and 513 and diode 519 to the point 533,placing the lefthand plate of capacitor 503 at substantially theintermediate potential of that point-- ie that capacitor will standcharged. When the pulse generator is dc-squelched by the removal of anysubstantial positive potential from terminal 543 the transistor 501 willforthwith assume a non-conductive condition, with effects as follows:

The assumption of non-conductive condition by transistor 501 rendersineffective the circuit 516-518, noted above to have been maintainingthe righthand plate of capacitor 504 at near negative supply potential,accordingly permitting the charging of that capacitor (righthand platepositive) through and at a rate controlled by the resistors 512-514 andthrough the input path of transistor 502 which is then renderedconductive by the charging current. The conductivity of 502 drops itscollector potential to near negative supply potential, invoking therapid discharge of capacitor 503 through the circuit 515-517, transistor502 and diode 507, after which the circuit 515-517 will maintain thelefthand plate of capacitor 503 at near negative supply potential andthat capacitor essentially discharged. The conductivity of transistor502 will continue until capacitor 504 has been charged to theintermediate potential of point 533, whereupon further charging isabruptly foreclosed by the diode 520 diverting the current flow fromthat capacitor to the point 533. The cessation of charging causestransistor 502 forthwith to assume a non-conductive condition.

The assumption of non-conductive condition by transistor 502 will invokean action, including conduction by transistor 501, identical with thatdescribed in the preceding paragraph excepting for the interchange oflefthand and corresponding righthand components. At the conclusion ofthat action transistor 501 will again become non-conductive, reinvokingthe action just as described in the preceding paragraph-and so on in acontinuous alternation continuing until the pulse generator isresquelched. Throughout the odd-numbered half-cycles of this alternationthe amplifying transistor will be nonconductive and the terminal 541thus at essentially regulated positive potentialthat terminal being atnear negative supply potential during the even-numbered halfcycles aswell as quiescently.

It will be observed that in the squelched condition the components ofthe pulse generator are maintained in substantially the same conditionas that in which they will be at the very end instead of anyeven-numbered half-cycle, with the results (i) that the first half-cyclefollowing de-squelching will invariably be one of conductivity oftransistor 502, and (ii) that the duration of that first half-cycle willbe essentially no different from that of any subsequent odd-numberedhalf-cycle. By adjustment of the variable resistors 514 and 513 theremay be controlled within limits the durations of the oddandeven-numbered half-cycles, respectively-4e. the dura tions of thepositive pulses at terminal 541 and of the inter-pulse intervals,respectively, each of which durations was above postulated to beapproximately 50 milliseconds.

In review of the earlier description above, there are d (specificallythree) digit conductors (i.e. 1, 2 and 3); c (specifically four)addresses conductors (Le. 10, 20, 30 and 40) selectively activatable byrespective switches (i.e. 13, 23 etc.); ncd (specifically twenty-four,11 being two) normally open electrical paths (i.e. 113, 114 344) underthe control of the digit conductors and the address conductors, eachcombination of one digit conductor and one address conductor whencontemporaneously activated effecting the closure of a respective n(specifically two) of the paths (eg the combination of digit conductor 1and address conductor 10 when contemporaneously activated effecting theclosure of the two paths 113 and 114); means, actuated as an incident tothe activation of one of the address conductors, for sequentiallyactivating the digit conductors in a predetermined sequence (e.g. 1, 2,3) thereby successively to close, it (specifically two) at a time, nd(specifically six) of said paths; and terminal-interconnecting means(i.e. the W and G conductors), with which the paths are selectivelyconnected (within CB) to render those terminal-interconnecting meanseffective in accordance with closures of those paths, for establishingpreselected interconnections of the electrical-system terminals Lthrough L4 and H0 through H3.

In compact review of the function of the apparatus, the closure (eithermomentary or longer) of the switch (eg 13 or 23) of one of the selectorunits (eg, 12 or 22) will result forthwith in the automatic tone-dialingof the telephone address which in the interconnection-establishing meansCB has been preselected, or programmed, for the associated addressconductor (e.g. the abovementioned designation 569 in the case ofaddress conductor 10, or 790 in the case of address conductor 20). Thistone-dialing will be completed in approximately (d- /z) O milliseconds(e.g. in approximately 250 milliseconds in the illustrated case whereind equals three). If a pair of selector units (as illustrated for thepair 32-42) be interconnected for the tone-dialing of a telephoneaddress of a greater number of digits, then the closure of the switch(e.g. 33) of the first unit of that pair will result forthwith in theautomatic tone-dialing of the telephone address which has beenpreselected, or programmed, for the pair of associated addressconductors (e.g. the address 1327, whose tone-dialing will be completedin approximately 350 milliseconds).

As has been brought out above, the illustration of the number 0 ofaddresses as four and of the number d of digits as three is purelytypical, and in practice other and usually larger numbers of addressesor digits or both may and usually will be used. It is interesting tonote that even though the number of digits be increased to seven, whichis of course a very common choice, the tone-dialing of any fullseven-digit telephone address will be completed in approximately 650millisecondsi.e. in less than twothirds of one second, and this inresponse to the merely momentary closure of a single switch, and with nopossibility of erroneous deviation from the sequence of integers whichhas been preselected, or programmed, for that switch.

It will of course be understood that the preselection, or programming,for any address conductor may be changed from time to time as the needsor desires of the user may dictate-such change requiring merely thealteration of the connections of the paths for that address conductorwithin the interconnection-establishing means CB.

FIGURES 1 through 3 and the foregoing detailed description havedisclosed the invention in a preferred embodiment in which theelectrical system is the tone-dialing oscillator TDO, with which is hasvarious special utilities already made apparent. In its broader aspects,however, the invention is not limited to use in connection with a systemof that particular form. By way of example FIG- URE 4, which is intendedfor optional substitution for the righthand portion of FIGURE 1,illustrates the invention in an embodiment wherein the electrical systemfor the transmission of a number of respective-integerrepresentingsignals, designated generally as ES, is of a quite different typei.e. ofthe general type schematically shown in FIGURE 6 (supplemented byvarious preceding figures) of an article by B. H. Geels and N. Schefferappearing in Philips Telecommunication Review, vol. 17, No. 1, August1956 at pages 3 et seq. and is described in that article and in othermaterial to which it makes reference.

In FIGURE 4 the electrical system ES includes a portion ESl comprising anumber (typically six) of variously interconnectible terminals T T T T Tand T of which T is grounded, and of which T T and T are connected-T andT first through respective oppositely poled diodes D and D -tl1rough acommon resistor R to one conductor M of a two-conductor line, and ofwhich T and T are connected through respective oppositely poles diodes Dand D and through a common resistor R to the other conductor M, of thatline. (A seventh terminal which would have been provided for diodelessconnection to resistor R in a fuller analogy to FIGURE 6 of the articleis absent because unnecessary.) The system ES also includes a portionESZ into which that line is connected, which includes suitable sourcesof power, which registers the sequence of integers signalled bysuccessively established interconnections of the terminals, and whichappropriately transmits (eg. over a line N) corresponding successiveinteger-representing signals of a nature not herein of importance. Withthe system BS1 the transmitter T and receiver or earphone E of thetelephone set are appropriately integrated. Thus. the line conductor Mmay be connected through normally closed relay contacts 691 hereinaftermentioned, through one of the sets of contacts of the cradle switch Sand through a resistor 694 to one extremity of the primary 696 of atransformer 695; the other line conductor M may be connected directly tothe other extremity of the primary 696; the earphone E may be connectedacross the secondary 697 of the transformer 695; and the transmitter Tmay be connected from the mid-point of the primary 696 both For theinteger: Interconnection between T and 1 T, 2 T and T 3 T 4 T and T 5 c6 T and T 7 T and T 8 T and T 9 T 0 T and T First it will be understoodthat for the transmission of various integer-representing signals fromthe electrical system ES the apparatus according to the invention mustin this embodiment effect terminal interconnections according to theimmediately preceding tabulation. As a secondary function, for reasonsbrought out in the article last above referred to, the normally closedcontacts 691 should be opened a few milliseconds after any particularinteger-representing interconnection of the terminals and should remainopen during the remaining period of that interconnection. As a tertiaryfunction the periods during which successive particular interconnectionsof the terminals are effected should be separated by appreciableintervals. FIGURE 4 shows the modifications of the apparatus of FIGURE 1appropriate to these functions; from FIG- URE 4 there are omitted, inthe interest of simplicity, muting arrangements such as shown in anddescribed in connection with FIGURE 1, though they could be incorporatedif desired.

In FIGURE 4, in full correspondence with FIGURE 1, there appear thedigit conductors 1, 2, and 3; the address conductors 10, 20, 30 and 40;the d (e.g. twenty-four) pairs of contacts 111, 112 341, 342respectively included in the 20d paths 113, 114 343, 344, a respective2d of those contact pairs forming parts of a respective one of therelays 11, 21, 31 and 41 therethrough to associate their respectivepaths with a respective one of the address conductors 10, 20, and the 2d(e.g. six) common conductors 173, 174, 273, 274, 373 and 374 eachincluded in a respective c of the paths; and the 2d pairs of contacts171, 172, 271, 272, 371 and 372, a respective two of those contact pairsforming parts of a respective one of the relays 170, 270 and 370therethrough to associate their respective paths with a respective oneof the digit conductors 1, 2 and 3. From the 2d contact pairs 171 372 acommon conductor 600 may connect all the 20d paths to theelectrical-system terminal T In FIGURE 4 theinterconnection-establishing means CB of FIGURE 1 is replaced by agenerally similar means CB comprising five conductors W W W W and Wrespectively connected to the terminals T T T T and T (replacing thefour conductors W1 through W4 and the three conductors G1 through G3 ofFIGURE 1), and Mad interconnection points each providing for theconnection of one of those five conductors with one of the 20d (e.g.twenty-four) paths 113, 114 343, 344 abovementioned-it being nowcontemplated that any one of those paths may be connected to any one ofthe conductors T through T by an actual connection at the point whereinFIGURE 4 that path crosses that conductor.

The paths 113 and 114, being a pair for the determination of the integerwhich expresses the first digit of the telephone address for which thefirst address conductor is programmed, will be connected to the oneconductor or two conductors which is or are appropriate to that integer;if that integer be 5 it is sufiicient that one of those two paths beconnected to the conductor W (the other being left unconnected or,harmlessly, connected to that same conductor). The paths 213 and 214,being a pair for the determination of the integer which expresses thesecond digit of that telephone address, will be connected to theconductor or conductors appropriate to that integer; if that integer be6 one of those two paths will be connected to the conductor W and theother to the conductor W Correspondingly the circuits 313 and 314 willbe connected to the conductor or conductors appropriate to the integerexpressing the third digit; if that integer be 9 one of those two pathswill be connected to the conductor W (the other being left unconnectedor, harmlessly, similarly connected).

The paths 123-124, 223-224 and 323-324, for the successive integers ofthe telephone address for which the second address conductor isprogrammed, will be connected according to similar principlesand so on.FIG- URE 4 by way of example shows the second address conductorprogrammed for the telephone address 790, the third programmed for 132and the fourth programmed for 734. In the manner thus outlined there isperformed the primary function of effecting the required terminalinterconnections.

The secondary function of opening the normally closed contacts 691 a fewmilliseconds after any particular integer-representing interconnectionof the terminals may be performed with the aid of the transistor 85,which is rendered conductive, just as in FIGURE 1, a few millisecondsafter the inception of each SO-millisecond pulse from the pulsegenerator PG. That transistor, since its FIGURE-1 function as such doesnot need to be performed with the electrical system ES, may in FIGURE 4be diverted to the function of opening contacts 691; for this purposeits collector may be connected to, and may control the current through,the coil 692 of a relay 691 of which the contacts 691 form a part.

The tertiary function of separating by appreciable intervals the periodsduring which successive particular interconnections of the terminals areeffected may be performed with the aid of an n-p-n transistor 685 whoseemitter may be connected to negative supply potential, whose base(connected through a high-valued resistor 684 to that emitter) may beconnected to the pulse-generator terminal 541, and whose collector maybe connected to and may control the flow of current through the coil 682of a relay 680 (the other end of that coil being connected to a positivesupply potential). The relay 680 may have normally open contacts 681interposed in series with the common conductor 679 through which currentis supplied to the coils of relays 170*, 270 and 370; the result of thisarrangement is that each of those relays can be operated only during anactual pulse from the pulse generatori.e. will be operated throughoutthe first 50 milliseconds only of the milliseconds throughout which itwould otherwise be operated, the remaining SO-milliseconds becoming aninterval between periods of successive particular interconnections ofthe terminals. This action also rounds out the performance of thesecondary function of the preceding paragraph, by bringing eachparticular interconnection of the terminals to an end before thecontacts 691 are re-closed.

While I have illustrated and described my invention in terms of aparticular embodiment thereof, it will be understood that I intendthereby no unnecessary limitations. Modifications in many respects willbe suggested by my disclosure to those skilled in the art, and suchmodifications will not necessarily constitute departures from the spiritof the invention or from its scope, which I undertake to define in thefollowing claims.

I claim:

1. In combination with an electrical system for the selectivetransmission of a number of respective-integerrepresenting signals,which system includes a plurality of variously interconnectibleterminals, the interconnection of said terminals determining thetransmitted signal: (I (a' being a plural integer) digit conductors; c(a being a plural integer) selectively activatable address conductors;ncd (n being an integer) normally open electrical paths under thecontrol of said digit conductors and said address conductors, eachcombination of one digit conductor and one address conductor whencontemporaneously activated effecting the closure of a respective n ofsaid paths; means, actuated as an incident to the activation of one ofsaid address conductors, for successively activating the digitconductors in a predetermined sequence thereby successively to close, itat a time, mi of said paths; and terminal-interconnecting means, withwhich said paths are selectively connected to render thoseterminal-interconnecting means efiective in accordance with closures ofthose paths, for establishing preselected interconnections of saidterminals.

2. The subject matter claimed in claim 1 wherein said electrical systemis a tone-dialing audio-frequency oscillator, wherein theinterconnection of said terminals determines the oscillators toneoutput, and wherein said terminal-interconnecting means are traversableby alter-' nating signal components.

3. The subject matter claimed in claim 2 wherein said terminals comprises (s being a plural integer) sets each of a plurality of variouslyinterconnectible terminals, and wherein n equals s.

4. The subject matter claimed in claim 1 wherein each of saidlast-mentioned interconnections serially includes one of said paths.

5. The subject matter claimed in claim 1 further including means,connected with said digit-conductor-activating means and responsive tothe completion of operation thereof, for ole-activating the previouslyactivated address conductor.

6. The subject matter claimed in claim 1 further including means forde-activating the previously activated address conductor after thesuccessive activation of said digit conductors and means connected with,and responsive to the de-activation of, that address conductor foractivating another of said address conductors.

7. The subject matter claimed in claim 2 further including means towhich a selected one of said paths may be connected for disabling theoscillator during the closure of that selected path.

8. The subject matter claimed in claim 2. further including means towhich a selected one of said paths may be connected for disabling theoscillator both during the closure of that selected path and during anyremainder, after such closure, of said sequence of digit-conductoractivation.

9. The subject matter claimed in claim 2 further including a pulsegenerator, and wherein said means for successively activating said digitconductors comprises electronic-stepping-switch means timed by saidpulse generator.

10. In combination with a tone-dialing audio-frequency oscillator whichincludes a plurality of variously interconnectible terminals, theinterconnection of said terminals determining the oscillators toneoutput: a plurality of digit conductors; a pulse generator; a steppingswitch, operatively connected with and timed by the pulse generator, foractivating the digit conductors in a predetermined sequence; means forestablishing preselected interconnections of said terminals, saidinterconnectionestablishing means being controlled by said digitconductors to establish a respective such interconnection as an incidentto the activation of each digit conductor; and means, operativelyconnected with and timed by the pulse generator, for periodicallyactivating and de-activating the oscillator.

11. The subject matter claimed in claim 10 further including means,operatively interposed between said pulse generator :and saidoscillator-activating and -deactivating means, for retarding the timingof the latter relative to that of said stepping switch.

12. The subject matter claimed in claim 10 wherein saidoscillator-activating and -deactivating means is operatively connectedwith and timed by said pulse generator in multiple relationship to saidstepping switch.

13. The subject nfltter claimed in claim 12 further including means,operatively interposed between said pulse generator and saidoscillator-activating and -deactivating means, for retarding the timingof the latter relative to that of said stepping switch.

14. The subject matter claimed in claim 10 further including means forshock-exciting said oscillator at the times of its activation.

15. The subject matter claimed in claim 10 further including a telephonetransmitter element locally connected with said oscillator, and meansfor incapacitating said transmitter element during the periods ofactivation of said oscillator.

16. The subject matter claimed in claim 10 further including a telephonereceiver element locally connected with said oscillator, and means forattenuating the action of said receiver element during the periods ofactivation of said oscillator.

References Cited UNITED STATES PATENTS 3,301,967 1/1967 Plyer 179-90KATHLEEN H. CLAFFY, Primary Examiner.

A. H. GESS, Assistant Examiner.

